Charge forming method and apparatus



June 5, 1962 B. c. PHILLIPS 3,037,751

CHARGE FORMING METHOD AND APPARATUS Filed July 20, 1959 2 Sheets-Sheet 1 73 INVENTOR: 5a

2 50 as EBRNARD [7. PHILLIPS.

I 120 7 72 74 54 BY Fri-5'- M m United States Patent Oflice 3,037,751 CHARGE FORMING METHOD AND APPARATUS Bernard C. Phillips, Toledo, Ohio, assignor to The Tillotson Manufacturing Company, Toledo, Ohio, a corporation of Ohio Filed July 20, 1959, Ser. No. 828,331 17 Claims. (Cl. 26135) This invention relates to a method of forming a combustible fuel and air mixture and charge forming apparatus for use with an internal combustion engine, and more especially to a charge forming apparatus embodying a diaphragm-controlled fuel inlet valve means wherein liquid fuel is delivered from a fuel reservoir or diaphragm chamber in the charge forming apparatus into an air and fuel mixing passage under the influence of aspiration or dilferential pressure established by air flow through the mixing passage, the method and apparatus of the invention involving the delivery of an increased amount of fuel into the mixing passage for engine accelerating purposes to temporarily enrichen the normal fuel and air mixture when the throttle is suddenly opened to increase the speed of the engine.

Carburetors or charge forming devices embodying a diaphragm-controlled fuel inlet means for a diaphragm chamber in the carburetor have come into extensive use for delivering combustible fuel and air mixture to twocycle engines of the types having particular utility for powering chain saws, outboard motors, lawnmower-s and the like, but such diaphragm carburetors up to the present time have not been extensively used for supplying combustible mixture to engines of the so-called four-cycle or Otto cycle type.

Diaphragm type carburetors, especially those for use with low horsepower internal combustion engines of the two-cycle type have been particularly successful by reason of certain characteristics of a two-cycle engine. In the operation of two-cycle engines, the fuel and air mixture is introduced into the crankcase of the engine and following crankcase compression of the mixture, the same is channeled into the cylinder and therein compressed by movement of the piston prior to the ignition or burning of the charge in the cylinder.

The crankcase of an engine of the two-cycle type usually contains an appreciable amount or residue of wet mixture or liquid fuel which, when the throttle of the charge forming device or carburetor is opened, provides an excess of liquid fuel or wet mixture for temporarily enrichening the charge delivered into the engine cylinder facilitating rapid acceleration of the engine when the throttle is quickly moved to full open or near open position. However certain types of two-cycle engines tend to function with a dry crankcase and lack an excess of liquid fuel or wet mixture in the crankcase for engine accelerating purposes.

Four-cycle engines are usually equipped with comparatively short intake manifolds or ducts for conveying combustible mixture from a charge forming device into the cylinders and practically no accumulation of liquid fuel or wet mixture is contained in the manifolds. In engines of this type any additional fuel for temporarily enrichening the mixture for engine accelerating purposes must be sup plied by means associated with the charge forming device or carburetor.

Heretofore the conventional float-type carburetor has been almost universally used for supplying combustible mixture to four-cycle engines as the float-type carburetor embodies a float-controlled fuel inlet valve which establishes a defined fuel level in a carburetor fuel chamber or bowl, and various means have been extensively used in float-controlled carburetors for delivering enrichened mixture to the manifolds. In most diaphragm type carbu- 3,037,? 51 Patented June 5, 1962 retors no predetermined fuel level is maintained thus rendering it difficult to provide for the temporary delivery of additional fuel to a mixing passage for engine accelerating purposes as is accomplished by gravity flow of fuel in carburetors embodying float-controlled fuel inlet valve means.

The present invention embraces a method of providing for the temporary delivery of additional liquid fuel into a mixing passage of a diaphragm type carburetor wherein a fluid pressure impulse is imparted to the diaphragm controlling the fuel inlet valve means under the influence of a sudden opening movement of the throttle valve for temporarily increasing fuel flow through the carburetor into the mixing passage to facilitate rapid engine acceleration.

The present invention embraces the provision of a charge forming apparatus of the diaphragm type adapted for use with two-cycle and four-cycle engines wherein an impulse is imparted to the fuel flow control diaphragm under the influence of the position of the throttle valve to promote temporary increase in the flow of liquid fuel into the diaphragm chamber and into the mixing passage to provide for enrichened mixture for engine accelerating purposes.

Another object of the invention is the provision of a charge forming apparatus or carburetor embodying a diaphragm-controlled fuel inlet means and equipped with a second diaphragm or movable means adapted to be influenced by a sudden opening of the throttle valve for transmitting a fluid pressure impulse to the fuel inlet control diaphragm to effect a momentary increase in the flow of liquid fuel through the diaphragm chamber into the mixing passage.

Another object of the invention is the provision of a novel method and apparatus for temporarily enrichening the fuel and air mixture in a charge forming device responsive to opening movements of the throttle valve, the method and apparatus being especially adaptable for use on [four-cycle engines where a temporary enrichenment of the mixture is imperative under increased load and speed conditions of the engine for proper operation.

Another object of the invention resides in the provision of means embodied in or associated with a carburetor or charge forming apparatus equipped with a diaphragmcontrolled fuel inlet valve which is substantially instantaneously responsive to sudden opening movements of the throttle valve in the mixing passage of the charge forming apparatus for rapidly supplying additional fuel into the mixing passage through a pressure impulse imparted to the fuel inlet controlling diaphragm.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE 1 is a top plan view of a charge forming apparatus or carburetor embodying the invention;

FIGURE 2 is a bottom plan view of the carburetor illustrated in FIGURE 1 with the fuel flow control diaphragm removed for purposes of illustration;

FIGURE 3 is a longitudinal section-a1 view taken substantially on the line 33 of FIGURE 1;

IGURE 4 is a transverse sectional view taken substantially on the line 4-4 of FIGURE 2;

FIGURE 5 is a bottom plan view of a modified form of carburetor embodying the invention;

FIGURE 6 is a longitudinal sectional view taken substantially on the line 6-6 of FIGURE 5;

FIGURE 7 is a top plan view of another form of carburetor embodying the invention;

FIGURE 8 is a side elevational view of the carburetor illustrated in FIGURE 7 with a portion of the construction shown in section;

FIGURE 9 is a longitudinal sectional view taken substantially on the line 9--9 of FIGURE 7;

FIGURE 10 is a transverse sectional view taken substantially on the line 1010 of FIGURE 7;

FIGURE 11 is a detail sectional view taken substantially on the line 1111 of FIGURE 8, and

FIGURE 12 is a sectional view taken substantially on the line 1212 of FIGURE 8.

Referring to the drawings in detail, and initially to the form of the invention illustrated in FIGURES 1 through 4, the charge forming apparatus or carburetor is inclusive of a carburetor body or body member 10 preferably of die cast construction formed with a mixing passage 12 into which liquid fuel is delivered and mixed with the air in the passage providing a combustible mixture for delivery to an internal combustion engine with which the carburetor may be used.

The mixing passage is formed with an air inlet 14, and a Venturi 16 having a choke band or restricted region 18. The carburetor body 10 is formed with a mounting flange 20 at the outlet end 15 of the mixing passage and is provided with openings 21. The outlet of the mixing passage is adapted to register with an intake manifold of a four-cycle type engine where the carburetor is used with a four-cycle engine, or is adapted to register with a port in the crankcase of a two-cycle engine where the carburetor is used with an engine of the latter type, the openings 21 accommodating bolts or other means for securing the mounting flange either to a manifold or an engine crankcase construction.

Disposed in the air inlet region 14 of the carburetor body 10 is a choke valve 24 of the disk type mounted upon a shaft 26 journaled for rotation in openings formed in boss portions provided on the carburetor body. The choke valve supporting shaft 26 is equipped with an arm or manipulating member 27 for manually rotating the shaft. The outlet region of the mixing passage is provided with a disk-type throttle valve 30 mounted upon a throttle shaft 32 journaled in suitable bores formed in the carburetor body 10.

The throttle shaft 32 is equipped with a manipulating arm or member 34, a coil spring 36 surrounding an exterior region of the shaft and engaging the arm 34 to normally bias or urge the throttle valve 30 toward engine idling or substantially closed position. An adjusting screw (not shown) is associated with the throttle shaft 32 for adjusting the idle position of the throttle valve 30. As particularly shown in FIGURES 2 through 4, the carburetor body is formed with a generally circular recess providing a relatively shallow fuel chamber 40 defined by a circular portion 42.

A flexible diaphragm or membrane 44 formed of impervious material resistant to deterioration by hydrocarbon fuels extends across the shallow fuel chamber 40 and forms a flexible wall of the chamber. Disposed between the circular periphery of the diaphragm 44 and the circular portion 42 is a sealing gasket 45 to provide a fluid tight seal between the periphery of the diaphragm and the carburetor body. An annular member or ring 46 engages the opposite peripheral face of the diaphragm 44 as particularly shown in FIGURES 3 and 4.

Extending across the circular region defined by the annular member 46 is a second diaphragm or pressure impulse producing means 50 formed of flexible impervious material and, in cooperation with the diaphragm 44, forms a second chamber 52 which provides an impulse region or chamber for purposes hereinafter explained. Disposed at the opposite side of the second diaphragm 50 is a closure plate or member 54 having a peripheral boss por- 4 tion 56 which engages the periphery of the second diaphragm 50 as shown in FIGURES 3 and 4.

The circular planar region or boss portion 42 is provided with a plurality of circumferentially spaced openings 58, and the ring 46 and plate 54 are formed with openings aligned therewith to accommodate securing screws 60, one of which is shown in FIGURE 4 threaded into the openings 58 for securing the diaphragms 44, 50, the annular member 46, the closure plate 54 in proper assembled position to the body 10 as shown in FIGURES 3 and 4. The circular boss portion 56 of closure member 54 defines a circular chamber 62 which is vented in the outlet region 15 of the mixing passage through the medium of ducts or channels 64 and 66, the ducts intersecting in the member 54 as shown in 53.

The chamber 52 is vented to the atmosphere through a metering passage or restricted duct 68 which is of very small size or area for a purpose to be hereinafter explained. The first diaphragm 44 provides a component of means for controlling the ingress or flow of liquid fuel into the chamber 40 from a fuel supply in accordance with the normal rate of delivery of fuel into the mixing passage 12. The fuel chamber 40 is unvented to the atmosphere and is actuated or flexed solely by aspiration or reduced pressure set up by the velocity of the air stream moving through the mixing passage.

The aspiration or suction in the chamber 40 is effective to cause delivery of fuel through fuel discharge or delivery passages or nozzles hereinafter described opening into the mixing passage 12. The diaphragm 44 is also actuated by impulse pressure set up or established in the chamber 52 under certain operating conditions as hereinafter explained.

The central region of the closure member or plate 54 is provided with a depending hollow boss portion 70, the hollow region accommodating an expansive coil spring 72. Disposed at each side of the second diaphragm 50 are thin metal reinforcing disks or plates 73 and 74 and a rivet or member 75 extends through openings in the plates and diaphragm. The expansive spring 72 bears against the disk or plate 74 on the lower side of the diaphragm 50 and normally flexes or maintains the diaphragm 50 in the broken line position shown in FIGURE 3.

An elongated recess 78 is formed in an upper wall defining the shallow fuel chamber 40 in the body 10 and accommodates a lever 80 formed of sheet metal, the lever 30 being provided intermediate its ends with a loop portion to accommodate a pin 82, shown in FIGURE 4, the pin 32 forming a fulcrum or pivotal axis for the lever 80. As shown in broken lines in FIGURE 2, the pin 82 is formed with a threaded portion 83 which is threaded into a bore formed in the carburetor body to facilitate assembly of the lever in the carburetor body.

Disposed at opposite sides of the first diaphragm 44 are metal disks 84 and 85 and a member or rivet 86 extends through openings in the disks and diaphragm. The head portion of the rivet 86 is adapted to be engaged by the long arm 83 of the lever 30. An expansive coil spring 90 disposed in a circular bore 91 engages the lever arm 88 and normally biases the arm 88 into engagement with the rivet 86 whereby movement of the diaphragm 44 effects pivotal movement of the lever 80. The short arm 92 of the lever St) is adapted to engage an end of a fuel inlet valve member or valve body 94.

The carburetor body 10 is formed with a threaded bore to receive a valve cage or valve guide fitting 96, the fitting being provided with a central bore adapted to loosely and slidably accommodate the valve member 94 which is preferably of rectangular cross-section. Arranged in a counter bore at the upper end of the fitting 96 is a valve seat or member 98 preferably formed of yieldable or semi-hard material such as neoprene or other suitable material which is resistant to deterioration by hydrocarbon fuels. The valve seat 98 is of annular shape and provides a fuel inlet port 100.

A sealing gasket 1112 is disposed between the end of the fitting 96 and a ledge formed at the end of the bore in the carburetor body accommodating the fitting. The valve member or body 94 is formed with a cone-shaped valve portion 104, the apex region of the valve portion 104 extending into the port 100 and cooperating with the valve seat 98 to regulate or control the flow of liquid fuel from a supply into the diaphragm chamber or fuel reservoir 40.

The carburetor body is formed with a boss portion 106 provided with a threaded bore to accommodate a threaded fitting 107 which is adapted to be connected with a fuel supply (not shown).

The body 10 is provided. with communicating passageways 108 and 109 through which liquid fuel from the supply flows to the port 100 in the valve seat 93. The fuel supply for the carburetor may be by gravity flow directly from a tank or receptacle, or the fitting 107 connected with a fuel pump for supplying liquid fuel under pressure to the carburetor. The port 100 in the valve seat 98 is of comparatively small diameter in order to present a minimum area of the valve portion 104 to the pressure of the incoming fuel in order to render the fuel control means extremely sensitive to minute pressure variations in the chamber 40.

The carburetor body includes ducts, channels or passages formed or drilled therein for conveying fuel from the fuel chamber 40 into the mixing passage 12. In the form shown in FIGURES 1 through 4, a main fuel delivery orifice or outlet 112 opens into the choke band 18 of the Venturi 16. The fuel delivery arrangement includes secondary or supplemental orifices 114 and 116 opening into the mixing passage providing means for delivering fuel into the mixing passage for idling and low speed engine operation. The main orifice 112 is for the pulpose of delivering fuel into the mixing passage for high speed engine operation.

The main orifice 112 is in communication with a bore or chamber 118 closed at its end by a plug 120. The carburetor body is formed with a threaded bore 122 adapted to threadedly receive a member 124 which is provided with a knurled knob or finger grip portion 125. The member 124 is provided with a stem 126 having a tapered extremity or valve portion 127 which extends into a bore 128 which is in communication with the bore 118 adjacent the main or primary fuel discharge orifice 112.

The bore or passage 122 in the carburetor body is in communication with the fuel chamber 40 by means of a port or duct 130 shown in FIGURE 2. Thus fuel enters the port 130 from the chamber 40 and flows past the tapered valve 127, bore 118 and through the main orifice 112 into the mixing passage for high speed engine operation. The fuel flow into the mixing passage takes place by reason of the aspiration or reduced pressure existent in the mixing passage during engine operation. By manipulating the valve member 124 the fuel flow through the main orifice may be regulated or metered.

The form of the invention of FIGURES 1 through 4 includes a secondary fuel delivery system by means of the orifices 114 and 116. The orifice 114 may be referred to as an idling orifice and serves to deliver fuel into the mixing passage at the engine side of the throttle valve 30 when the throttle valve is in substantially closedor engine idling position as shown in FIGURE 3. Means is provided for metering or controlling the flow of fuel to a chamber, recess or region 134 for delivery through the secondary orifices 114 or 116. The recess or region 134 is isolated from direct communication with the fuel chamber 40 by means of a Welsh plug 136.

The body 10 of the carburetor is formed with a threaded bore or passage 140 in which is adjustably mounted a second threaded valve member 142 provided with a knurled finger grip or knob 143 for adjusting the position of the member 142 for regulating or metering fuel flow to the secondary orifices. The member 14 2 is provided with a tenon portion 144 terminating in a tapered valve portion 145 which extends into and cooperates with a bore 146 of reduced diameter which is in communica tion with the bore 140*. The bore 146 opens into the auxiliary chamber or region 134 adjacent the secondary orifices.

The passages 122 and 140 are in communication by means of a channel or duct 148 shown in FIGURE 2. The channel 148 is fashioned by drilling a passage from the mounting flange region of the carburetor into the passage 122 as shown in FIGURE 2, and the entrance of the drilled passage closed by a plug 151 An air bleed passage 152 opens into the mixing passage and establishes communication with the recess or region 134 adjacent the secondary orifices, as shown in FIGURE 3. Through this arrangement air is bled into the fuel delivered through the secondary orifices 114 and 116.

The operation of the carburetor or charge forming device illustrated in FIGURES 1 through 4 is as follows:

The operation of the carburetor will first be described where the throttle valve 30 is moved comparatively slowly from one position to another viz. as from an idling position to an intermediate position and full open or high speed engine operation position. The main fuel chamber or reservoir 30 is unvented and is therefore subservient to the influence of aspiration or reduced pressure existent in the mixing passage 12 during engine operation.

When the throttle is in idling position, that is, substantially closed position as illustrated in FIGURE 3 a high suction or aspiration is existent on the engine side of the throttle 30 and is effective to cause fuel to be delivered from the chamber 40 through the idling orifice 114. Whenever fuel is being delivered into the mixing passage through any orifice or orifices, the amount of fuel in the chamber 40 is depleted and the aspiration or reduced pressure is effective to flex the diaphragm 44 upwardly as viewed in FIGURES 3 and 4.

As the diaphragm 40 moves upwardly, the rivet or member 86 exerts upward pressure upon the lever swinging the lever in a counterclockwise direction as viewed in FIGURE 4. This action permits the valve body 94- and valve portion 104 to move downwardly, whereby fuel flows from the supply through the passages 1118, 109 and port into the fuel chamber 46. The valve body 94 being of polygonal shape in cross-section facilitates fuel flow into the chamber 49 thence through an orifice or orifices into the mixing passage. The rate of delivery of fuel to the secondary orifices is regulated or metered by adjust ing the position of the valve member 142.

When the throttle valve 30 is moved gradually toward open position, the secondary or low speed orifice 116 is brought into operation delivering fuel from the region 134 into the mixing passage for low speed engine operation. During partial open throttle condition, fuel may be de livered into the mixing passage from both the secondary orifices 114 and 116. When the throttle 30 is moved gradually toward open position, the air moving through the Venturi 16 increases in velocity.

When the air velocity in the Venturi 16 is substantial, the influence of aspiration or reduced pressure causes fuel to be delivered from the fuel chamber 40 past the high speed adjusting or metering valve 127 through the main orifice 112 into the Venturi. When this condition obtains a high engine speed, the discharge of fuel through the secondary orifices 114 and 116 usually ceases, although there may be a period in the operation of the engine when fuel delivery from the orifices 114 and 116 may overlap the delivery of fuel from the main orifice 112.

When the throttle valve 30 is again moved to nearly closed or idling position fuel delivery through the main 7 orifice 112 ceases and fuel is then delivered through the second idling orifice 114 into the mixing passage.

The operation of the carburetor under conditions wherein a temporary enrichenment of the mixture is established by the delivery of additional fuel into the mixing passage in excess of the normal amount is as follows:

As previously mentioned when the throttle valve 30 is in substantially closed position, that is, engine idling position, a reduced pressure or high aspiration exists in the mixing passage on the engine side of the throttle valve viz. at the right side of the valve as viewed in FIGURE 3.

In this position of the throttle valve under engine idling operation, the suction or aspiration in the mixing passage is effective through the passages 64 and 66 to establish reduced pressure in the chamber 62 beneath the second diaphragm 50. Due to the substantial area of the diaphragm 50, the reduced pressure in the chamber 62 fiexes the diaphragm to its lower position as indicated in full lines in FIGURE 3 and compresses the spring 72 to store potential energy in the spring.

When the operator suddenly opens the throttle valve 3&1 to rapidly increase the speed of the engine, the pressure effective on the passages 64 and 66 and chamber 62 is substantially instantaneously increased, and the potential energy is the compressed spring 72 flexes the diaphragm 50 upwardly at a rapid rate. As the vent 68 for the charm ber 52 between the diaphragm 5t} and 44 is of small size, the rapid upward movement of diaphragm 50 compresses the air in chamber 52 and exerts a pressure impulse on the under side of diaphragm 44 forcing the fuel inlet control diaphragm 44 upwardly thus opening the valve 9'4 and permitting substantial increase in flow of fuel into the chamber 40.

This action substantially instantly increases the amount of fuel delivered through the main orifice 112 into the mixing passage 12. The additional amount of fuel delivered into the mixing passage temporarily enrichens the mixture delivered to the engine and hence causes a rapid acceleration in the speed of the engine. After a short period of time, the pressure in the intermediate chamber 52 between the diaphragms is equalized or becomes atmospheric by air escaping through the restricted vent 68 whereby the diaphragms 44 and 50 return to their positions of normal operation.

When the throttle is moved from open or near open position to an engine idling or substantially closed position, the pressure on the engine side of the throttle is again reduced substantially and this reduced pressure or aspiration is transmitted to the chamber 62 through the passages 64 and 66 to again cause the diaphragm St} to be flexed downwardly compressing the spring72.

Thus whenever the throttle valve 30 is moved to a closed or nearly closed position, the spring '72 is compressed and conditioned with potential energy in readiness to effect an upward pressure impulse, through the medium of the air in chamber 52, upon the fuel inlet control diaphragm 44 to deliver automatically an increased amount of fuel through the main orifice 112 whenever the throttle 30 is quickly moved to a full open or near open position.

Through this method of storing potential energy in a member responsive to aspiration or difierential pressures in the mixing passage, fuel flow is automatically increased through the main orifice above that normally delivered to the mixing passage whenever the throttle valve 30 is suddenly moved toward a full open or near open position providing an enrichened mixture for rapidly accelerating the engine. This result is effected by reason of the differential pressures existent in different zones of the mixing passage under the changing conditions at varying engine speeds and throttle positions.

The rapidity and magnitude of the impulse imparted to the fuel flow control diaphragm 44 by upward movement of the second diaphragm under the potential energy of the spring 72 may be regulated and controlled by varying the size of the air vent 68 in the member 46. By decreasing the size of the vent 68 the magnitude of the pressure impulse on the fuel control diaphragm 44 may be increased and of a longer period of duration during which an augmented amount of fuel flows through the main orifice 112.

If the vent 68 is enlarged, the fluid pressure impulse acting against the diaphragm 44 will be of decreased magnitude and of shorter duration due to a more rapid equalization of pressure in the intermediate or impulse chamber 52. Whenever the pressure is equalized in the chamber 52, the fuel delivery from the chamber 40 into the mixing passage continues under normal operating conditions.

FIGURES 5 and 6 illustrate a modified form of carburetor arrangement embodying a pressure impulse fuel flow acceleration means of the invention. In this form the carburetor body It) is substantially the same shape and character as the carburetor illustrated in FIGURES 1 through 4. This form of carburetor is formed with a mixing passage having a portion of circular cylindrical shape of substantially uniform cross-sectional area from the air inlet region 14 to a flared outlet region 162 at the mounting flange end of the carburetor.

The mounting flange 20' is of the same character as that shown at 2% in FIGURE 1 and is adapted to be secured either to a manifold of a four-cycle engine or to the crankcase of a two-cycle engine, depending upon the type of engine with which the carburetor is used. The mixing passage at the air inlet end is provided with the choke valve 24' mounted upon a shaft 26. The throttle valve 30' is mounted upon a rotatable shaft 32'. The arrangement is provided with the fuel inlet control diaphragm 44- and an impulse diaphragm 50' which is associated with a spring 72' in the same manner as shown in the construction illustrated in FIGURES 1 through 4.

The diaphragm 44 is engaged by a lever 80 arranged for cooperation with a fuel inlet valve in the manner shown in FIGURE 4. Aspiration or reduced pressure in the mixing passage 16% is transmitted through passages 64' and 66 to the chamber 62' between the diaphragm 50' and the closure plate 54' whereby the chamber 62 is under the influence of differential pressures in the mixing passage to cause movements of the diaphragm 50 setting up pressure impulses effective to flex the fuel inlet control diaphragm 44 in an upward direction for the purpose of accelerating fuel flow into the mixing passage.

The annular member 46' is provided with a restricted air vent 63 for equalizing the pressure in the intermediate chamber 52'. Fuel flows through the inlet valve arrangement into the fuel chamber 40' as controlled by the position of the diaphragm 44.

In this form of construction, the main fuel orifice 166 is in communication with the auxiliary chamber or region 134' and the secondary or idle orifice 168 is arranged to open into the mixing passage at the engine side of the throttle valve 30 when the latter is in engine idling or nearly closed position.

An air bleed tube 170 is angularly disposed in the manner shown in FIGURE 6 and opens toward the air inlet of the mixing passage to admit air into the recess or chamber 134' for admixing with the fuel delivered into the mixing passage. In this arrangement a single adjustment or metering means is provided for regulating normal fuel flow from the fuel chamber 40' to the secondary chamber or recess 134'.

As shown in FIGURE 5, a port 174 establishes communication between the fuel chamber 40 and a passage or bore 176 formed in the body. The bore is formed with a threaded portion to accommodate an adjustable valve member 178 of the general character of that shown at 142 in FIGURE 2, the valve member 178 being provided with a knurled finger grip portion 180 to facilitate manual adjustment. The bore or passage 176 is in communication 9 with the recess or chamber 134' by means of a passage or duct 182 of reduced diameter.

A tenon portion of the valve member 178 is provided with a tapered or needle valve portion 186 which extends into and cooperates with the metering passage or restriction 182 for regulating fuel flow into the chamber 134'. Adjustment of member 178 regulates the normal fuel flow to both the main orifice 166 and the low speed or idling orifice 168.

The operation of the form of carburetor construction shown in FIGURES and 6 is as follows: With the throttle valve 30' in engine idling or nearly closed position, fuel flows from the fuel chamber 40 through the port 174, passage 176, past the needle valve 186 through the restricted passage 182 and chamber 134' and into the mixing passage through the secondary orifice 168. When the valve 34) is gradually opened the velocity in the central region of the mixing passage 160 increases and fuel is delivered from the main orifice 166 although some fuel may continue to flow into the mixing passage through the secondary orifice 168.

When the throttle 30' is in idling or nearly closed position the aspiration or substantially reduced pressure on the engine side of the throttle valve 30', that is, at the right side of the throttle valve as viewed in FIGURE 6, the pressure in the chamber 62 is substantially reduced elfec-ting a compression of the spring 72'. When the valve 38 is suddenly moved to open or nearly open position, the pressure adjacent the outlet end of the mixing passage increases and this increase in pressure is communicated to the chamber '62v The potential energy stored in the spring 72' moves the diaphragm 50 rapidly in an upward direction imparting, through the medium of the confined air in chamber 52', an upward impulse to the control diaphragm 44, immediately increasing the amount of fuel flowing into the fuel chamber 40' and hence increasing the amount of fuel delivered into the mixing passage either through the main orifice 166 or the secondary orifice 168 to temporarily enrichen the fuel and air mixture delivered to the engine.

In a short period of time, however, dependent upon the size of the air vent 68' the pressure in the intermediate chamber 52 is equalized and, when this occurs, the fuel control diaphragm 44' returns to its normal position influenced thereafter by the aspiration or pressure existent in the mixing passage to deliver fuel in a normal amount either through the main orifice 166 or the secondary orifice 168 or both depending upon the speed of operation of the engine. Under all conditions of operation of the carburetor, some air is bled into the fuel through the tubular air bleed 172.

A carburetor embodying a modified form of the invention is illustrated in FIGURES 7 through 12 of the drawings. In this form, the carburetor body 218 is similar in shape to the body shown in FIGURE 1. The carburetor includes a mounting flange 220 which is adapted to be secured to the manifold of an engine of the fourcycle type or with the crankcase of an engine of the twocycle type. The mixing passage is inclusive of an air inlet region 214, a Venturi construction 216 and a mixture outlet region 217 at the engine side of the throttle valve 230.

The air inlet is provided with a choke valve 224 mounted upon a rotatable shaft 226 and the outlet region 217 of the mixing passage provided with a disk-type throttle valve 230 mounted upon a rotatable throttle shaft 232, The choke valve shaft 226 is provided with an arm 227 for manipulating the choke valve and the throttle valve shaft 232 is provided with a manipulating arm 234 for operating the throttle valve. A coil spring 236 surrounds a portion of the shaft 232 exteriorly of the carburetor body, the spring being engaged with the arm 234 to normally bias the throttle valve toward a closed position.

The carburetor body 210 is formed with a shallow fuel chamber 240, and a diaphragm 244 extends across the chamber 240 and forms a flexible wall of the fuel chamber. The diaphragm 244 is engaged at its peripheral region by a circular member 246, the peripheral region of the member 246 engaging the diaphragm 244 to secure the same in sealing relation with a circular planar surface 242 on the body 210, a gasket 245 being disposed between the diaphragm and the body 210 to effect a seal.

The fuel inlet control means is illustrated in FIGURE 10 and is inclusive of a lever 280, the long arm 288 of the lever being engaged by a rivet 286 at the central region of the diaphragm 244. The lever is fulcrumed intermediate its ends on a pivot or fulcrum pin 282. The short arm 290 of the lever is engaged with a lower end of a valve member or valve body 294, the upper end of the valve body being provided with a tapered valve portion 304 which cooperates with a ported valve seat 298. The port in the valve seat 298 is in communication with a fuel inlet fitting 307 through communicating passageways 308 and 309.

A coil spring 291 engages the lever 280 to normally bias the lever in a counterclockwise direction, as viewed in FIGURE 10, urging the valve portion 304 to valve closing position. During fuel flow from chamber 240 into the mixing passage, aspiration or reduced pressure set up in the chamber 240 from the mixing passage is eflective to elevate the diaphragm 244, which action swings the lever 280 counterclockwise to permit the valve 294 to move downwardly, opening the port in the seat 298 whereby fuel from a supply (not shown) flows through the fitting 307, passages 308, 309 and the port in the valve seat into the chamber 240'.

The valve member 294 is loosely and slidably mounted within a fitting 296 threaded into a bore in the carburetor body In this form of the invention an impulse diaphragm is provided but is actuated by mechanical means such as by movement of the throttle valve. The body of the carburetor is provided with channels and ducts adapted to convey fuel from the fuel chamber 240' into the mixing passage. The main orifice 315 opens into the choke band 218 of the Venturi as shown in FIGURE 9.

Disposed adjacent the main orifice is a fitting 316 adapted to contain a ball check valve 317 to prevent back bleeding through the main orifice duringfue-l discharge from the secondary orifice means. The fitting 316 is provided with a reduced tubular tenon portion 318 which extends into a well or supplemental chamber 320 shown in FIGURE 9. The chamber 320 is isolated from the fuel chamber 240 by means of a Welsh plug 341. An air bleed passage 342 is in communication with the air inlet region 214 and with the supplemental chamber or well 320 as shown in FIGURE 9.

The body 210 is formed with a bore 322 having a threaded portion to accommodate a threaded valve member 324 provided with a knurled finger grip or knob 326 for adjusting the position of the valve member 324. The valve member is provided with a stem 327 provided with a tapered needle valve portion 328 which extends into and cooperates with a restricted passage 329 for regulating the flow of fuel to the main or high speed orifice 315. A passage or duct 330, shown in FIGURE 11, establishes communication between the fuel chamber 244] and the bore 322 for feeding fuel into the bore 322 and into the supplemental chamber or well 328.

As shown in FIGURES 9 and 12, the secondary system includes an idling orifice 345 and a low speed orifice 347 which open into a small chamber 348 formed in the body of the carburetor, The chamber 348 is isolated from the reservoir 240 by a Welsh plug 349.

Formed in the body 218 is a threaded bore 352 which accommodates a valve body 354 having a threaded portion threaded into the bore 352, the Valve member 354 being provided with a knob 356 for adjusting the position of the valve member. The valve member 354 is formed with a stem portion 358 having a tapered or needle-like 1 l extremity 360 which extends into and cooperates with a restricted passage 362 which opens into the small chamber 348 of the secondary fuel delivery system to meter fuel flow to the secondary orifices.

As particularly shown in FIGURE 12, a passage or channel 364 is in communication with the chamber 320 and the bore 352 for conveying fuel from the well or supplemental chamber 320 to the bore 352 past the needle valve 360 in passage 362 into the chamber 348 for delivery into the mixing passage through the secondary orifices 345 and 347. The channel or passage 36-4 is drilled into the body and the entrance of the drilled passage closed by means of a plug 366 shown in FIGURE 12.

In the form of the invention shown in FIGURES 7 through 12, the arrangement for effecting delivery of additional fuel into the mixing passage for accelerating purposes is initiated by mechanical means such as by movement of the throttle toward open position. With particular reference to FIGURES 9 and 10, it will be seen that the second or impulse diaphragm 250 is disposed between the circular member 246 and a closure member 254.

In this form of construction the impulse chamber comprises two compartments 252 and 252', the compartments being partially separated by means of an inwardly extending web 370 formed on the circular member 246 as shown in FIGURES 9 and 10, a communicating passage 372 being provided in the web whereby the compartments 252 and 252' together provide an impulse chamber.

The closure member 254 is fashioned to provide a chamber 376 in which is disposed a lever 378 fulcrumed intermediate its ends upon a pin or shaft 380. Arranged at each side of the impulse diaphragm 250 are metal disks, a rivet or member 382 extending through the disks as shown in FIGURE 10, the head of the rivet or member 382 engaging one arm of the lever 378.

As particularly shown in FIGURE 10, the carburetor body 210, the circular member 246, and a flange region of the closure member 254 are provided with aligned bores to accommodate a shaft or rod 384 shown in FIG- URE 10. One end of the rod 384 engages an aim of the lever 378, and the other end of the rod terminates in engagement with a cam surface 388 formed on the throttle shaft 232. As shown in FIGURE 8, the shape of the cam surface 388 on the throttle shaft 232 is configurated whereby upon rotation of the throttle shaft to move the throttle valve 23%) toward an open position, the cam surface 388 moves the rod or shaft 384 downwardly causing the lever 378 to be swung in a counterclockwise direction, as viewed in FIGURE 10, and exert a rapid upward movement of the impulse diaphragm 250.

This movement of the impulse diaphragm in an upward direction slightly compresses the air in the intermediate or impulse chamber 250 and causes an upward flexure of the fuel flow control diaphragm 244, which action swings the lever 280 to a position whereby the valve 294- moves downwardly and admits additional fuel into the chamber 240, thereby providing for additional fuel delivered through the main orifice 315.

As shown in FIGURE 9, the intermediate or impulse chamber 252 is vented into the air inlet region 214 of the carburetor body by means of interconnected passageways 389, 389, and the metering restriction 390, the latter being of minute size. The function of venting the chamber 252 through a metering restriction 390 is to delay the equalization of pressure in the impulse chamber 252 at the time a pressure impulse is imparted to the fuel flow control diaphragm 244 by positive upward fiexure of the impulse diaphragm 250.

A comparatively weak spring 392 is disposed between the web 37 on the circular member 246 and the impulse diaphragm 250 to maintain the rivet or member 382 in continuous contact with the lever 378 and the rod 384 in continuous contact with the cam surface 338 formed 12 011 the throttle shaft 232. The chamber 376 is vented to the atmosphere through an opening or passage 377.

The normal operation of the carburetor shown in FIG- URES 7 through 12 is essentially the same as the normal operation of the carburetor illustrated in FIGURES 1 through 4 with the exception that the ball check member 317 disposed in the fitting 316 adjacent the main orifice functions to prevent back bleeding through the main orifice into the secondary fuel discharge system when the latter is delivering fuel during idling or low speed engine operations.

The ball check 317 serves an additional purpose in that by closing of the main orifice a portion of the fuel flowing through the chamber 328 to the secondary orifice system enters and remains in the supplemental chamber 320 as an accelerating charge for subsequent delivery through the main orifice.

When the operator moves the throttle rapidly to an open position, the cam surface 388 simultaneously depresses the rod 384- swinging the lever 378 to flex the impulse diaphragm 250 upwardly, compressing the air in the intermediate chamber 252 which imparts a pressure impulse on the fuel control diaphragm 244. The diaphragm 244 is flexed upwardly as viewed in FIGURE 10 permitting the valve 294 to open and admitting more fuel into the fuel chamber 240.

The admission of added fuel into the chamber 240 provides for delivery of an increased amount of fuel into the mixing passage through the main orifice 315 and this is supplemented by the charge or amount of fuel present in the well 320 which is immediately discharged by aspiration into the mixing passage when the throttle valve is moved to an open position. After a short period of time, the pressure in the intermediate chamber 252 is equalized through the air vent provided by passages 388, 389 and restriction 390 so that the fuel control diaphragm 244 thereafter normally controls the ingress of fuel into the chamber 24-0 in accordance with the rate of delivery of the fuel through the main orifice or through the secondary orifices.

It is desirable that the air vent restriction 390 be made small enough so that the pressure in the impulse chamber 252 is equalized in a comparatively short period of time. The length of the acceleration impulse may be modified by changing the area of the vent restriction 390 and by changing the contour of the cam surface 388 associated with the throttle shaft 232.

It is to be understood that a bellows or similar means may be employed in lieu of the impulse diaphragm 250 and arranged to be operated by means associated with the throttle shaft in a manner to provide a fluid pressure impulse effective on the fuel control diaphragm 244. From the foregoing it will be apparent that the forms of the invention provide for temporary enrichenment of a fuel and air mixture for an internal combustion engine which is efficient and reliable in operation for accelerating purposes. The pneumatic or pressure impulse accelerating arrangement of the invention is position free i.e. is adaptable for operation in all angular or inverted positions.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

1 claim:

1. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a throttle valve in the mixing passage, a diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, said diaphragm being responsive to differential l3 pressures in the mixing passage, means actuated by said diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, and means responsive to movement of the throttle valve toward open position to impart a pressure impulse to the diaphragm for admitting additional fuel through the fuel inlet intothe fuel chamber to accelerate the rate of fuel delivery through the orifice into the mixing passage.

2. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a shallow recess, a throttle valve in the mixing passage, a diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber responsive to differential pressures in the mixing passage, means responsive to movement of the throttle valve toward open position to impart a pressure impulse to the diaphragm for admitting additional fuel into the fuel chamber and increasing the rate of fuel delivered through the orifice into the mixing passage, and means for regulating the duration of the pressure impulse.

3. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a shallow recess, a throttle valve in the mixing passage, a diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, said diaphragm being responsive to differential pressures in the mixing passage, means actuated by said diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, an air chamber, means operative upon rapid movement of the throttle valve toward open position to increase the pressure in the air chamber and thereby impart a pressure impulse to the diaphragm for admitting additional fuel into the fuel chamber to accelerate the rate of fuel delivery through the orifice into the mixing passage.

4. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a shallow recess, a throttle valve in the mixing passage, a first diaphragm forming with said recess, an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said diaphragm responsive to differential pressures in the mixing passage for controlling flow of liquid fuel from a supply into the fuel chamber, a second diaphragm disposed adjacent to and spaced from the first diaphragm, said diaphragms defining opposed walls of an impulse chamber, and means effective upon rapid movement of the throttle valve toward open position to impart movement to the first diaphragm through the impulse chamber for admitting additional fuel into the fuel chamber and increasing the rate of fuel delivered through the orifice into the mixing passage.

5. Charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a first diaphragm forming with said recess an unvented fuel chamber, a throttle valve in the mixing passage, means including a channel for conveying liquid fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, fuel inlet valve means controlled by movement of said diaphragm for regulating fuel flow from a supply into the fuel chamber, a second diaphragm forming .with said first diaphragm an impulse chamber, and spring means engaging the second dia- 14 phragm and rendered operative upon rapid movement of the throttle valve toward open position to increase the pressure in the impulse chamber effective on said first diaphragm to increase flow of fuel from the supply through the fuel chamber and channel into the mixing passage.

6. Charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a first diaphragm forming with said recess an unvented fuel chamber, a throttle valve in the mixing passage, means including a channel for conveying liquid fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, fuel inlet valve means controlled by movement of said diaphragm for regulating fuel flow from a supply into the fuel chamber, an impulse chamber, said diaphragm forming a wall of the impulse chamber, a second diaphragm forming another wall of the impulse chamber, means rendered effective upon movement of the throttle valve toward open position for moving said second diaphragm to transmit an impulse to said first diaphragm through the air in the impulse chamber to increase flow of fuel from the supply through the fuel chamber and channel into the mixing passage, and a metering restriction for venting said impulse chamber.

7. Charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a first diaphragm forming with said recess an unvented fuel chamber, a throttle valve in the mixing passage, means including a channel for conveying liquid fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, fuel inlet valve means controlled by movement of said diaphragm for regulating fuel flow from a supply into the fuel chamber, an air chamber, said diaphragm forming a wall of the air chamber, a second diaphragm forming another wall of the air chamber, said air chamber being vented through an air metering restriction, and spring means responsive to rapid opening movement of the throttle Valve to effect movement of said second diaphragm to increase the pressure in said air chamber to impart an impulse to said first diaphragm through the medium of the air in the air chamber to increase flow of fuel from the supply through the fuel chamber and channel into the mixing passage, the size of said air metering restriction determining the duration of the impulse effective on said diaphragm.

8. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a shallow recess, a throttle valve in the mixing passage, a first diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said first diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, said first diaphragm being responsive to differential pressures in the mixing passage, a second diaphragm, said diaphragms being spaced and defining opposed walls of an air chamber, a closure plate exteriorly of the second diaphragm and forming therewith a compartment, duct means establishing communication between the compartment and the mixing passage, a spring in said compartment in engagement with the second diaphragm adapted to control the position of said second diaphragm, and vent means for said air chamber.

9. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a throttle valve in the mixing passage, a first diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the miX- ing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said first diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, said first diaphragm being responsive to differential pressures in the mixing passage, a second diaphragm spaced from and disposed in parallelism with the first diapragm and forming with said first diaphragm an air chamber, means rendered effective upon movement of the throttle valve toward open position for moving said second diaphragm to compress air in said air chamber to actuate the first diaphragm and increase fuel flow into the fuel chamber and into the mixing passage, and restricted vent means in communication with the air chamber for determining the duration of increased pressure in the air chamber.

10. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a shallow recess, a throttle valve in the mixing passage, a first diaphragm forming With said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said first diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, said first diaphragm being responsive to differential pressures in the mixing passage, a second diaphragm, said diaphragms forming opposed walls of an air chamber, a member engaging the second diaphragm, means responsive to movement of the throttle valve toward open position for effecting movement of said member and second diaphragm to establish increased pressure in said air chamber to actuate the first diaphragm and increase fuel flow into the fuel chamber and into the mixing passage, and restricted vent means in communication with the air chamber for determining the duration of increased pressure in the air chamber.

11. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a throttle valve in the mixing passage, a shaft supporting the throttle valve, a first diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, a fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said first diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber responsive to differential pressures in the mixing passage, a second diaphragm, an air chamber formed between the diaphragms, means actuated by the throttle shaft for moving said second diaphragm to transmit a pressure impulse by the air in the air chamber to the first diaphragm.

12. A charge forming apparatus including, in combination, means formed with a fuel and air mixing passage and a recess, a throttle valve in the mixing passage, a shaft supporting the throttle valve, a first diaphragm forming with said recess an unvented fuel chamber, an orifice opening into the mixing passage for delivering fuel from the fuel chamber into the mixing passage by aspiration in the mixing passage, 21 fuel inlet formed in said means in communication with the fuel chamber, a valve for the inlet associated with and actuated by said first diaphragm for controlling flow of liquid fuel from a supply into the fuel chamber, said first diaphragm being responsive to differential pressures in the mixing passage, 21 second diaphragm, an air chamber formed by the diaphragms, and a lever arranged to be actuated by movement of the throttle shaft for moving said second diaphragm to transmit a pressure impulse to the first diaphragm through the air in the air chamber.

13. The method of temporarily increasing fuel flow into an air fuel mixing passage for supplying combustible mixture to an internal combustion engine having a throttle valve including establishing air flow in the passage, communicating the aspiration set up by the air flow to an unvented fuel chamber of variable volume, normally regulating the rate of flow of fuel from a supply into the fuel chamber by aspiration in the passage in accordance with the rate of delivery of fuel into the mixing passage, and establishing an air pressure impulse upon rapid opening movement of the throttle valve in the mixing passage effective to temporarily change the volume of the fuel chamber to increase fuel flow into the mixing passage and provide an eniichened mixture in the mixing passage, and dissipating the air pressure providing the impulse to restore normal regulation of the rate of fuel flow from the supply into the mixing passage.

14. The method of forming combustible mixture for an internal combustion engine and temporarily increasing fuel flow into an air and fuel mixing passage having a throttle valve including establishing air flow in the passage, transmitting reduced pressure caused by the aspiration set up by the air flow to a flexible membrane of a fuel chamber, normally regulating the rate of flow of fuel from a supply into the fuel chamber by relative movement of the membrane by aspiration in the passage in accordance with the rate of delivery of fuel into the mixing passage, and establishing a pressure impulse in an air chamber effective on the membrane upon rapid opening movement of the throttle valve in the mixing passage for temporarily changing the volume of the fuel chamber to increase fuel flow into the mixing passage and provide an enrichened mixture in the mixing passage, and admitting air into the air chamber to equalize the pressure and restore normal regulation of the rate of fuel flow from the supply through the fuel chamber into the mixing passage.

15. The method of forming combustible mixture for an internal combustion engine and temporarily increasing fuel flow into an air and fuel mixing passage having a throttle valve including establishing air flow in the passage, transmitting pressure of aspiration set up by the air flow in the mixing passage to a variable volume fuel chamber, normally regulating the rate of flow of fuel from a supply into the fuel chamber by the aspiration in the passage in accordance with the rate of delivery of fuel into the mixing passage, and establishing a fluid pressure impulse upon rapid opening movement of the throttle valve in the mixing passage effective to temporarily change the volume of the fuel chamber to increase fuel flow into the mixing passage and provide an enrichened mixture in the mixing passage.

16. The method of forming a combustible fuel and air mixture for an internal combustion engine for normal operation and for enrichening the mixture for acceleration purposes including flowing air through a mixing passage having a throttle valve therein, communicating the differential pressure established by air flow in the mixing passage to a variable volume fuel chamber for delivering fuel from the chamber through a channel into the mixing passage, normally regulating the rate of flow of fuel from a supply to the fuel chamber by varying the volume of the fuel chamber by the pressure differential in the mixing passage to establish a normal rate of delivery of fuel into the mixing passage, and establishing a pressure impulse exteriorly of the fuel chamber effective to temporarily reduce the volume of the fuel chamber upon rapid opening of the throttle valve in the mixing passage to temporarily increase the flow of fuel from the supply into the fuel chamber and from the fuel chamber into the mixing passage to enrichen the mixture in the mixing passage for engine accelerating purposes, and dissipating the pressure impulse independently of the position of the throttle valve.

17. The method of forming a combustible fuel and air mixture for an internal combustion engine for normal operation and for enrichening the mixture for acceleration purposes including flowing air through a mixing passage having a throttle valve therein, communicating the differential pressure established by air flow in the mixing passage to a movable surface of a variable volume fuel chamber for delivering fuel from the chamber through a channel into the mixing passage, normally regulating the rate of flow of fuel from a supply to the fuel chamber by varying the volume of the fuel chamber by the pressure differential in the mixing passage to establish a normal rate of delivery of fuel into the mixing passage, establishing a pressure impulse exteriorly of the fuel chamber and efiective upon a flexible surface of the chamber to temporarily reduce the volume of the fuel chamber upon rapid opening of the control valve in the mixing passage to temporarily increase the flow of fuel from the supply into the fuel chamber and from the fuel 18 chamber into the mixing passage to en-richen the mixture in the mixing passage, and dissipating the pressure impulse independently of the position of the throttle valve to restore normal rate of fuel delivery into the 5 mixing passage.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,387,271 Kittler et a1 Oct. 23, 1945 2,601,975 Hunt July 1, 1952 2,823,905 Brown Feb. 18, 1958 2,841,372 Phillips July 1, 1958 

